Cold Hardiness Evaluation of 20 Commercial Table Grape ( vitis Vinifera L.) Cultivars

The objectives of this study were to compare cold hardiness (CH) of 20 field-grown grapevine (Vitis vinifera L.) cultivars at four stages: Nov., Jan., Mar. and Apr., and to investigate the relationship between CH and soluble carbohydrates, proline, phenolic compounds and water content changes during acclimation and deacclimation stages. After exposure to various freeze test temperatures, cane LT50 values were estimated using electrolyte leakage and Tetrazolium stain test. CH of all cultivars studied increased with the overall trend of declining temperatures from Nov. through Jan., after which the canes began to deacclimate from Mar. and gradually lost CH in Apr.; overall LT50 means were -15.06, -23.73, -22.42 and -12.08, respectively. A relatively high variation of CH was shown in Jan., when ranged from -20.76 to -26.43ºC. In this sampling stage, cultivars were classified as hardy (CH = -24.5 to -26.5; 'Moukhtchaloni', 'Volgo-Don', 'Druzhba', 'Khalili', 'Bidaneh Qermez', 'Bidaneh Sefid' and 'Monaqa'), moderately hardy (CH = -22.5 to -24.5; 'Fakhri Zoudras', 'Asgari', 'Peykani', 'Siahe Qarabaq', 'Qareh Shahani', 'Galin Barmaqi', 'Mirzaei', 'Thompson Seedless' and 'Fiesta') and least hardy (CH = -20.5 to -22.5; 'Flame Seedless', 'Shirazi', 'Perlette' and 'Ruby Seedless'). The pattern of soluble carbohydrates, proline, and phenolic compounds changes were highly consistent with the LT50 profile and cold hardy cultivars accumulated higher osmoregulants compared to others. Our results are valuable to viticulturist to select suitable cultivars for sustainable production in cold zones and to the grape breeder to advance grape CH programs.